I've been using the "get friends" app with no problems so far, turned over 200 in a few hours of sitting around waiting. Probably many more to come when I next log in.
A good trick is to join all the "mafia wars" and "mob wars" groups and post a big "ADDD MEEEEE" message. You'll get hundreds of adds from people asking to play mob wars, just ignore the application requests. Theres also a few "add me" groups that work. Use a picture of a hot girl and leave ditzy, blonde and provocative comments on guys walls. I get lots of adds from randomers with mutual friends.
EDIT: Just hit exactly 300 friends, and facebook is yet to rear it's ugly head